Best Product – What Size Cordless Power Tool Batteries are You Using or Buying?

Milwaukee M18 CP3 Ah High Output Battery

When you buy a cordless power tool kit, your battery choices are usually already made for you. There are different reasons why users might buy additional battery packs. Maybe you prefer to buy bare tools, you’re expanding your cordless tool set, replacing older batteries, or simply want more batteries.

So, for those of you who are buying cordless power tool batteries, what size(s) are you choosing?


If you’re not buying new batteries, which ones would you buy? Which battery sizes are you currently using?

The reason I ask is because the selection process has never been more complicated, and I have a feeling that it’s things can only get more so.

Having choices are great! But are there too many choices right now?

Shown above is a Milwaukee M18 CP 3.0Ah battery pack. Is it a better choice than the XC 3.0Ah battery pack? I think so. What about Milwaukee’s M18 compact 2.0Ah battery – does it replace that too? What about the XC 4.0Ah battery – would you choose this compact 5-cell 3.0Ah battery over the 4.0Ah battery built with 10 Li-ion cells?

If you need help deciphering things, I put together a primer on Milwaukee M18 batteries, and nothing has changed since then.

As an aside, it has been nearly 3 years since Milwaukee released a new M18 battery pack; what do you suppose they’re working on now?

Milwaukee M18 Battery Pack Lineup

I like to use Milwaukee’s M18 batteries as an example, but most pro-grade 18V/20V Max cordless power tool brands now offer battery packs in similarly varied form factors. Makita seems to be the only exception, but their new XGT 36V/40V Max lineup does feature larger cells in select batteries.

So, with Makita’s 18V line, the choice is easy – you can buy compact (5) cell batteries or higher capacity (10) cell batteries, with different charge capacity (amp-hour) ratings.

Learn more about amp-hours:

Okay, so the way things used to be, there was compact and higher capacity batteries.

Now, you have compact batteries with matching or higher charge capacities compared to physically larger batteries.

Dewalt 20V Max vs FlexVolt Battery Comparison 2021

Dewalt’s 20V Max lineup, for instance, has a (10) cell 5Ah battery, a (10) cell 6Ah battery that’s physically a little larger, and a (15) cell FlexVolt battery that’s even larger, but with a smaller footprint than the (10) cell battery.

If you want to put classify Dewalt or other brands’ batteries, there are different intersecting tiers, which is where things get messy.

With Dewalt 20V Max, you have compact (5) cell batteries – 1.3Ah, 1.5Ah, and 2.0Ah, “standard” (10) cell batteries – 3.0Ah, 4.0Ah, and 5.0Ah, larger form factor (10) cell batteries – compact 3.0Ah, compact 4.0Ah, 6.0Ah, 8.0Ah, and now 10.0Ah, and also (15) cell FlexVolt batteries in 6.0Ah, 9.0Ah, and 12.0Ah sizes. A new 15.0Ah FlexVolt battery is coming soon.

In another post, a reader said they considered Milwaukee’s M18 battery series to be more straightforward. They are, but things can be confusing for new users. There are compact batteries, standard 10-cell batteries, 5- and 10-cell batteries with High Output larger form factor battery cells, and also the High Demand 15-cell batteries.

Other brands have their own special differentiations, with fewer options overall contributing to the appearance of simplicity.

Bosch, for example, gives their larger cell batteries Core18V and ProFactor designations.

I keep thinking that some less popular battery sizes will eventually be phased out, such as 10-cell 3.0Ah batteries, but perhaps there’s still a marketing need for them in value-priced combo kits.

As for all of the others, how to choose one over another? Generally, a larger form factor battery pack can match the performance of a smaller form factor battery of the next-higher tier. That is, a 5-cell “High Output” style battery is supposed to be able to deliver the power requirements – but not necessarily the runtime – of standard-styled 10-cell batteries.

Things used to be simple. If you want longer runtime, step up to a battery with higher charge capacity. There was no overlap, there were simply two physical battery sizes and an easily deciphered scale of increasing charge capacity. You paid more for longer runtime, and could also calculate a dollar per amp-hour ratio to get the most bang out of your buck.

How do you choose batteries now? You can still approach the decision according to charge capacity and cost per amp-hour, but battery sizing has become an increasingly untethered factor.

Despite having the latest and greatest batteries at my disposal, I still have a fondness for 5.0Ah batteries, and that seems strange to me.

I like compact higher output batteries for some tools, such as lightweight hand vacs and cordless work lights, higher output 10-cell batteries for heavier tools where dealing with a little more weight pays for a lot longer runtime, and 15-cell batteries for power-hungry equipment that I don’t want to have to take too many breaks from.

I think that maybe I’m moving away from compact 2.0Ah batteries, since they only serve lightweight compact tools while compact high output batteries are a little more versatile. I can take a compact 3.0Ah battery, for instance, and use it with a compact drill or impact driver, and then move it to power a brushless circular saw or oscillating multi-tool.

So, I tend to use compact higher output batteries in place of the most compact batteries, and also in medium-duty tools that smaller batteries aren’t well-suited for.

But, there are also some times when those smallest 18V-sized batteries are useful.

Maybe things would easier if there were fewer battery size options for each different cell configuration or form factor, but users like having both lower priced and higher capacity options with similar form factors. 4.0Ah batteries did not make 3.0Ah batteries obsolete, and when 5.0Ah batteries came out, they simply joined their physically like-sized siblings.

Which battery size do I use? That’s a good question, and one I’m not sure I could answer with confidence. Sometimes I’m picky, other times it doesn’t matter. Most of the time it depends on the tool, or my whim.

My must-have-cannot-part-with list includes one from every single size/form factor of battery. I own quite a few batteries – mainly whatever comes with purchased tool kits, and they are complemented with samples of nearly every size and capacity.

I know that “at least one of every size” isn’t typical, and maybe that complicates things. I’m curious about the decisions you guys have made or are making with respect to battery selection.

Sometimes this is a passive decision – you get what you get in kits and promo bundles – but a lot of users also deliberately select different batteries to suit their specific needs. Other times, decisions could be made based on price.

All that said, what are your cordless power tool battery preferences? What sizes do you use, and which are you buying (or would be buying)?

Are there any sizes that you’ve been avoiding? For example, is there any reason to buy 10-cell 4.0Ah batteries anymore?

I had 18V/20V Max systems in mind for the sake of this discussion, but similar considerations can also apply to 24V Max and other like-classed cordless power tool lines, albeit usually with few options.